Radiolabeled immunoglobulin therapy (RIT) of human cancer continued to show considerable promise in the clinical and laboratory studies. Clinical trials using RIT are producing 50% complete remission rates in Hodgkin's disease at Johns Hopkins, and other institutes report excellent response with B-cell lymphoma. The response of other tumors is less pronounced. The laboratory studies that have been completed under this research program have not only identified mechanisms that influence the therapeutic ratio of RIT,but also offer specific research directions that may offer improved effects of RIT on a wider spectrum of human tumors.